She was a maid of honour and lady in waiting to Queen Elizabeth I, as was her sister Frances Howard, Countess of Kildare.
She married Sir Robert Southwell (1563—12 October 1598) of Woodrising, Norfolk, on 17 April 1583. He was the son of Sir Thomas Southwell and his second wife Mary Mansell, a daughter of Sir Rice Mansell (1487–1559).
Sir Thomas Southwell had a daughter with his third wife Nazareth Newton (d. 1583), another Elizabeth Southwell, who was a Maid of Honour to Queen Elizabeth. She was a mistress of Robert Devereux, 2nd Earl of Essex and mother of Walter Devereux, who married Sir Barentine Moleyns or Molyns of Clapcot.
After Robert Southwell's death in November 1598 Elizabeth Howard was left "a rich widow", and there was a rumour she would marry Sir William Woodhouse of Waxham, a cousin of her fellow courtier Lady Walsingham.
She became a lady of the Privy Chamber to Anne of Denmark in 1603. Her daughter, Elizabeth Southwell, was also a maid of honour to Anna of Denmark. After 1608 her daughters Frances and Katherine were gentlewomen of the Privy Chamber. A "Mrs Southwell", who made an unsuccessful trip to meet the queen in Scotland in May 1603, mentioned in the letters of Captain John Skinner from Berwick-upon-Tweed, was Anne Southwell, an author, the wife of a Sir Thomas Southwell.
She walked in procession at the funeral of Anne of Denmark in 1619, listed as "Lady Kencleven".
She died in 1646 and was buried at Greenwich.
Christopher Sutton, rector of Woodrising dedicated his Disce Mori (1600) and Disce Vivere (?1604) to Lady Southwell, and his Godly Meditations on the Most Holy Sacrament (1613) to her daughters Frances and Katherine.
Portraits of Elizabeth Howard, her mother Catherine Carey, and her daughter Elizabeth Southwell were included in a sale at Cowdray Park in 2011.
Her children included;
- Charles Southwell (2 February 1588 - 23 April 1588), buried at Reigate where the Howard family lived at Reigate Priory.
- Thomas Southwell (d. 1648), married Margaret Fuller.
- Elizabeth Southwell (1584-1631), maid of honour to Queen Elizabeth in 1599 meant to replace Mary Radcliffe, although the latter stayed on. She danced in the masque at the marriage of Henry Somerset, 1st Marquess of Worcester in June 1600. She was also maid of honour to Anne of Denmark, and third wife of Robert Dudley. She wrote an account of the death of Queen Elizabeth. She was buried in San Pancrazio, Florence where there was formerly a Latin inscription including her age, 37 years. Her portrait is drawn in an Italian armorial.
- Frances Southwell, gentlewoman of the privy chamber to Anne of Denmark, married Sir Edward Rodney of Rodney Stoke, Somerset, at Denmark House in 1614. The Earl of Rutland gave a wedding present of a gilt bowl and cover worth £21.
- Katherine Southwell, gentlewoman of the Privy Chamber to Anne of Denmark, who married Greville Verney, 7th Baron Willoughby de Broke in 1618.
- Robert Southwell.
- Margaret Stewart, married Sir Matthew Mennes of Sandwich.
- Alan Davidson, 'MOLYNS, Michael (c.1601-at least 1662), of Clapcot', The History of Parliament: the House of Commons 1604-1629, ed. Andrew Thrush and John P. Ferris, 2010.
- Norman Egbert McClure, Letters of John Chamberlain, vol. 1 (Philadelphia, 1939), pp. 52, 64, 70.
- HMC Salisbury Hatfield, vol. 15 (London, 1930), pp. 74-5, 90-1, 105-6, 388: Victoria Burke 'Anne, Lady Southwell', in George L. Justice, Nathan Tinker eds, Women's Writing and the Circulation of Ideas (Cambridge, 2002), pp. 97-8.
- Edmund Lodge, Illustrations of British History, vol. 3 (London, 1838), p. 89, Lodge has failed to correctly identify the couple in his footnote
- John Nichols, Progresses of James First, vol. 3 (London, 1828), p. 540.
- Daniel Lysons, The Environs of London: Counties of Herts, Essex & Kent, vol. 4 (London, 1796), p. 475.
- J. Endell Tyler, Disce Mori: Learn to Die, by Christopher Sutton (London, 1839), pp. viii-xi.
- Weiss Gallery, Tudor and Stuart Portraits (2013), pp. 30-41.
- Mill Stephenson, 'A list of Monumental Brasses in Surrey', Surrey Archaeological Collections, vol. 32 (1919), p. 70.
- Michael Brennan, Noel Kinnamon, Margaret Hannay, The Letters of Rowland Whyte to Sir Robert Sidney (Philadelphia, 2013), p. 377.
- Michael Brennan, Noel Kinnamon, Margaret Hannay, The Letters of Rowland Whyte (Philadelphia, 2013), pp. 498, 501: Arthur Collins, Letters and Memorials of State, vol. 2 (London, 1746), p. 201: Roy Strong, The Cult of Elizabeth (London, 1977), pp. 28-43.
- Catherine Loomis, The Death of Elizabeth I: Remembering and Reconstructing the Virgin Queen (New York, 2010), pp. 83-5.
- John Temple Leader, Life of Sir Robert Dudley (Florence, 1895), pp. 9-10, 146.
- Norman Egbert McClure, Letters of John Chamberlain, vol. 1 (Philadelphia, 1939), p. 512.
- HMC Rutland vol. 4 (London, 1905), p. 500.